1. Field of the Invention
This invention relates to an oil returning mechanism of an evaporator for an air conditioner equipped with, for example, a variable capacity type cooling medium compressor.
2. Description of the Prior Art
In general, the lubrication of a cooling medium compressor for an air conditioner is performed by utilizing a lubricating oil in a cooling medium. This lubricating oil is flowed into a condenser and an air conditioner from a cooling medium compressor together with a cooling medium during the operation of the air conditioner and the lubricating oil within the compressor is reduced. Therefore, the oil flowed into the condenser and evaporator is somehow required to be returned to the compressor.
The prior art intended to meet with such requirements is disclosed, for example, in Japanese Utility Model Early Laid-open Publication No. 47-7168 and Japanese Patent Early Laid-open Publication No. 55-165452. Of these Publications, the former discloses an oil returning mechanism in which a cooling medium tube between a cooling medium compressor and a condenser is cut apart, a baffle plate is interposed between opposite communication ports, a capillary tube connected to a bottom portion of a main body is connected to the cooling medium tube between the cooling medium compressor and evaporator in order to feed the lubricating oil separated from the medium into the cooling medium compressor. On the other hand, the latter discloses an oil separator interposed between a cooling medium compressor and a condenser, in which a multistage throttle is provided to a bottom portion of its main body, and the throttle is communicated with the cooling medium compressor through a passage, so that the quantity of the lubricating oil separated therein for returning to the compressor can be adjusted through the throttle.
However, these conventional apparatuses have such problems as that since oil is separated using a pressure energy of a cooling medium and such separated lubricating oil is collected, these apparatuses are practically applicable only to a cooling circuit in which a cooling medium is high pressure and cannot be employed for a low pressure circuit such as, for example, vicinity of an evaporator where the oil separating and oil returning functions are lowered. Particularly, these problems are serious for an air conditioner equipped with a variable capacity type cooling medium compressor which has been expected to be widely prevailed in recent years, because the oil returning quantity to the cooling medium compressor is extremely reduced during its very small load operation and the lubrication is worried.
The present invention was accomplished in order to solve these problems.